By Ernest Scheyder

Exxon Mobil has agreed to develop more than 6,100 lithium-rich acres in Arkansas with Tetra Technologies Inc, the second move this year by the oil giant for control of assets needed to produce the electric vehicle battery metal.

Exxon's rapid expansion into the lithium sector comes amid growing interest by traditional energy companies and others into emerging technologies that aim to boost global supply of the ultralight metal.

Tetra, which produces chemicals for water treatment and recycling, earlier this week said it had signed an agreement with a company known as Saltwerx to develop 6,138 acres of salty brine deposits in Arkansas that are filled with lithium and bromine, although it provided few additional details.

Saltwerx is a subsidiary of Exxon, according to two people familiar with the matter. Exxon acquired it earlier this year when it bought a neighboring Arkansas parcel of 100,000 acres from Galvanic Energy. Galvanic remains an independent, privately held company and is not affiliated with Tetra or Exxon.

Representatives for Tetra were not immediately available to comment. Exxon declined to comment.

Financial terms were not disclosed. Neither company provided a production or development timeline, although Exxon will be contributing about 2,000 acres and Tetra about 4,100 acres to the partnership. Certain details still need to be finalized.

By partnering with Exxon, Tetra gains a large partner with capital to help it produce bromine, which is used in flame retardants, from the acreage. Tetra currently buys bromine from Lanxess to produce a material used by Eos Energy Enterprises to manufacture batteries.

Exxon, meanwhile, gains access to yet another U.S. supply of lithium as the country rapidly expands its EV supply chain. Both companies plan to file an amended application to develop the brine deposits later this year with Arkansas officials.

Exxon would need to chose at least one direct lithium extraction (DLE) technology to filter the metal from the Arkansas brine, although such technologies are largely unproven at commercial scale. Reuters reported earlier this month that Exxon has held talks with International Battery Metals and EnergySource Minerals about licensing DLE technology.

Tetra said in November it has been investigating various DLE technologies, but had not signed any agreements.

Tetra had previously agreed to lease more than 27,000 acres in Arkansas to Standard Lithium to produce lithium. Standard has started preliminary work on development of that project.

(Reporting by Ernest Scheyder; Editing by Chris Reese)